Studies will continue on the enzymes Beta-hydroxy-Beta-methylglutaryl-CoA (HMG-CoA) reductase, cholesterol 7-alpha-hydroxylase, acetyl-CoA carboxylase and the fatty acid synthetase complex of rat liver. Studies with HMG-CoA reductase will be concerned with the properties and structural organization of this enzyme, the identification of the mechanisms of regulation of the activity of this enzyme (including the identification of the mechanisms by which glucagon and insulin regulate its activity), the purification to homogeneity of the enzymatically-inactive species of this enzyme, and the purification of the enzyme system that converts enzymatically active HMG-CoA reductase to inactive enzyme. Studies on cholesterol 7-alpha-hydroxylase will be concerned largely with attempts to purify this enzyme to homogeneity and with assays for the activity of this enzyme in animals subjected to different nutritional or hormonal states. Investigations with acetyl-CoA carboxylase will concentrate upon attempts to establish the mechanism by which glucagon and insulin regulate the activity of this enzyme. Phosphorylation-dephosphorylation is suspected as a mechanism. Studies on the fatty acid synthetase will be concentrated on the isolation, purification and translation (in a reticulocyte lysate system) of the mRNA for this enzyme.